Electrical apparatus



NOVQ24, 1931. n J, M KENDALLv 1 I 1,833,750

ELECTRICAICL APPARATUS Filed Jun 1, 1927.

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xa I I I .Ihvenbor James M. Kehdall by- I His Attorney Patented Nov. 24, 1931 UNITEDISTATE'SIPATENT JAMES M. KENDALL, or sco'rIA, NEW YORK, AssIGNoE TO GENERAL EL o'r Ic com r i a CORPORATION oE'N wfYo K 1 ELECTRICAL ABBAE-A-TUSP I?" f r Application filed. June 1,

My invention relates to sound-reproducing apparatus, and has for itsprincipalobject the provision of an improved arrangement for obviating the disagreeable sound that is 5 likely to occur in searching for a distant 'station when a' radio-receiving apparatus adjusted for maximum sensitivity is tuned through a local transmitting station.

It is desirable that an apparatus utilized.

1 to preventthe disagreeable blast of sound produced by tuning a sensitive radio-receiving device through'a loud .local station be capable of limiting the'input voltage of the receiver to a predetermined valueand have ;no effect on the received impulses until this value is attained; Inaccordance with my invention, this result is produced by means comprising a pair of unilaterally conductive or rectifying elements connected in shunt to the receiver input circuit and arranged to transmit current only whenthe voltage of this circuit exceeds a predetermined value.

My invention will be better understood from the following description when considered in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

Referring to the drawings, Fig. 1 is a wir ing diagram of a receiving apparatus wherein my invention has been embodied, and Figs. 2 and 3 illustrate certain details in the operation of this apparatus. 7. T w p This apparatus comprises a telephone device or loud speaker 1 which is provided with i an operating winding 2 and a field winding 3.

Current is supplied to the operating winding 2 from a supply circuit't'through atransformer 5, a space-discharge device 6, and the.

field winding 3which is interconnected with ;a pair of condensers 7 and 8 to form a filter whereby fluctuations in the anode supply voltage of the device 6 are obviated. Connected in shunt to the'anode circuit'of the device 6 andtransfor ner 5 is an impedance device shown as a resistor 9 provided with from a radio amplifying-and detectingwap- V paratus which may be energized by curren't; i supplied through the various. taps of there- 19 27 Ts'era1 9w92. l

is applied to the grid circuit .of thedevice 6.

i The output current ofthedevice 6fisiinodu 'lated bypotential impulses applied to input transformer ll through input leads sistorc9 or'in-any other suitableQmanner.

; In the: present 2 example, the "secondary. I. of transformer llis included in the grid circuit of device 6 .Whereby the leads, 12:1 am connected with the grid circuit and voltage impulsesare supplied to said grid circuit fromthe inputleads 12. Thedetecting and amplifying part of'the apparatus connected to the leads 12 has been omitted from the drawings totion In order to limit the-voltage etween the input leads 12 to apredetermined value, they ail facilitate aniunderstanding of theinvenare" arranged to be interconnected. through means comprislnga switch 13, a condenser '14, and. a pair of carborundum crystals 15'and 16 which are interconnected through a section 17ofthe-resistor 9 to form a closed loop circuit.

Itv should be understood that the} condenser 14 is providedfor excluding from the crystals 15 and 16 direct current which 1 i would otherwise tend toflow through the oil cuit 12, and thatthe crystals 15a'nd 16are.op-

positely connected so that. the overload curi j rent of the input circuit is transmittedbe tween theleads1 2through oneof the crystals in one direction and through the otherc'rys ntalkin the opposite direction.

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L ,.The operating characteristics; of eh efcrys j tals 15 and 16 are illustratedby FigslQ a d 3, Asjindicated byFig, 3, there is a-con -gi 'siderable voltage range within which no cur-i rent is transmitted through the crystal At oneend of this ran e, however, the! current t ransj mitted through the crystal increases veryrapidly while the voltageis maintained substantially constants purpose of :the I resistor section 17 is top-rovidea bias poten "'tia-lwhereby the proper relation ismaintain'ed between the operation of the-crystals of the resistor'scction'fl is indicated by the horizontal distance 0 which eXtendS'sUbsta-n- .ti'ally equal distances on: either side of the f origin. .0.

' Th'eLcrystals' 15 and'16 have no eiiect on the potential of the input transformer 11 so long,

as the input voltageapplied to the circuit 12 1' is maintained within the limits determined by cuits, input leads for said circuit, an

impedance device connected between the 'terininals; ofsaid output circuit, a pair Of'LlIli-i laterally conductive elements. interconnected through a section of-said impedance device to form a closed loop connected in shunt to .said input leads, and connections whereby'a part of the potential drop of said impedance device is applied to said grid circuit.

In witness whereof, I have hereunto set myhand this 31st day of May, 1927! l I JAMES M. KENDALL.

I l the biasvoltage of theresistorQsectiont 17. l/Vhen theselimits are exceeded in either di oppositely connected in shunt to said input rection, however, current is transmitted.

through one or the other ofthecryst'alsand the input voltage of the device 6 is limited to avalue'which does not producea disagreeable sound when a sensitivea-mplifying and de- .tec ting apparatus connected to the leads 12 is tuned through a stronglocal station inlsearch ing for a distant station. It will be apparent that the bias potential applied between the crystals 15*and16 may be derived from; any suitable source other than the resistor 9 and that theswitch13 need be closed only while tuningthe; apparatus to the frequency of the 3 station which it is desired to receive.

' VVhatI claim as new and desire to secure 7 i by Letters Patent of the United States, is, 1. The combination of a space-discharge device provided with a grid circuitand in put leads connected therewith,, a direct current supply means connected to the output circuit of said device, and apair of carborundum crystals interconnected through said supply means and arranged to maintain the voltage V between" said input leads within predetermined'limits. V

2. The, combination of a'space-discharge 5 device provided witha grid circuit, and input leads'connected therewith, a direct current source of potential, apair of unilaterally conductive elements arranged to be intercon necte'dwith said sourceto form a closedloop circuit therewith, each of said elements being.

leads,'and means for precluding the transmission'otdirect current between said source and said input circuit.

7 3. The combination oi alspace-discharge device" provided w1th'gr1d' "and output 'cire "cuits, input leads-for said gridcircuitsyan H I i device providediwith grid and output cirimpedance device connected between th'e'ter'-' v.

' minalsof said output circuit, a'nd apair or ,unilaterally conductive seleinents' interconliected'through a section of said impedance device to form a {closed loop tconnected i'n shuntto said input leads.

1-. l'lhe combination of a space-discharge no V 

